ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-6-225-2006The impact of ice uptake of nitric acid on atmospheric chemistryvon KuhlmannR.12LawrenceM. G.11Max-Planck-Institute for Chemistry, Department of Airchemistry, Mainz2now at: German Aerospace Center (DLR), Bonn2701200661225235This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article is available from http://www.atmos-chem-phys.net/6/225/2006/acp-6-225-2006.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/225/2006/acp-6-225-2006.pdf

The potential impact of the uptake of HNO<sub>3</sub> on ice on the distribution of
NO<sub>y</sub> species, ozone and OH has been assessed using the global scale
chemistry-transport model MATCH-MPIC. Assuming equilibrium uptake according to
dissociative Langmuir theory results in significant reductions of gas phase
HNO<sub>3</sub>. Comparison to a large set of observations provides support that
significant uptake of HNO<sub>3</sub> on ice is occurring, but the degree of the
uptake cannot be inferred from this comparison alone. Sensitivity simulations
show that the uncertainties in the total amount of ice formation in the
atmosphere and the actual expression of the settling velocity of ice particles
only result in small changes in our results. The largest uncertainty is likely
to be linked to the actual theory describing the uptake process and the value
of the initial uptake coefficient.
The inclusion of non-methane hydrocarbon
chemistry partially compensates for the absence of HNO<sub>3</sub> uptake on ice when this is neglected
in the model.
The calculated overall effect on upper tropospheric ozone concentrations and
the tropospheric methane lifetime are moderate to low. These results support a
shift in the motivation for future experimental and theoretical studies of
HNO<sub>3</sub>-ice interaction towards the role of HNO<sub>3</sub> in hydrometeor surface
physics.